Erectile dysfunction (ED) has a significant impact on male mentality and physiology. It has been found that an inhibitor of PDE5 can effectively treat ED, such as Cialis from Eli Lilly and Company, whose chemical structure is shown as follows:

PDE5 inhibitors were found to improve erectile dysfunction caused by a variety of factors, and as for the onset time, there is no significant difference among various PDE5 inhibitors. However, in respect of the half-life, there is a greater difference among these pharmaceutical compounds. For example, Cialis has a half-life of up to 24-36 hours in body, while Viagra from Pfizer and Levitra from Bayer both have half-life of about 4-5 hours.
Because of different half-life of a pharmaceutical compound, patients having different ages and different physical conditions will select pharmaceutical products with different half-lives to meet different requirements. However, there is a greater difference among the above-mentioned PDE5 inhibitors in half-life. Therefore, there is an urgent need for a novel PDE5 inhibitor.